ABB LST100 Operating Instructions Manual page 19

6 Calibration
An easy-to-use, 2-point calibration enables the best
possible accuracy by calibrating the measurement
to two known good points.
There are two types of errors: offset and gradient.
– Offset error
The error at close range is equal to the error at maximum
range. In this case the "c" value in the equation y=mx+c
must be corrected.
10.1 ft.
Measured
distance
1.1 ft.
1 ft.
Real distance
– Gradient error
A small error at a close range becomes larger
as the range increases. In this case the "m" value
in the equation y=mx+c must be corrected.
10.1 ft.
Measured
distance
1.01 ft.
1 ft.
Real distance
The speed of sound is linear, enabling calibration to be
performed using only 2 known points. This provides sufficient
information to calibrate LST100.
6.1 Calibration procedure
Calibration can be performed on site if the tank dimensions
are known. This gives best results as it ensures the instrument
is calibrated to the intended installation. Alternatively, the
calibration can be performed before installation by pointing
the sensor at a known target.
1. Log on to the LST100 as described in Section 4.3,
Configuring the digital communications . The welcome
screen is displayed.
y=mx+c
2. Select 1. Easy Setup from the main menu. Ensure that
Operate Mode is set to Distance.
Enter B to return to the main menu.
10 ft.
3. Select Calibration from the main menu. Ensure that
Enable User Calibration is set to NO. This disables any
existing calibration to avoid errors in the new calibration.
y=mx+c
Enter B to return to the main menu.
10 ft.
LST100 – Ultrasonic level transmitter | OI/LST100-EN 19